Magnifying glass



Dec. 31, 1935. G JAECKEL 2,026,176

MAGNIFYING GLAS S Filed June 5, 1954 Faye y Figa fig Fq'gf Patented Dec.31, 1935 A I MAGNIFYING GLASS Georg .laeckeL Berlin-Zehlendorf,Germany,- assigner to the hrm Sendlinger Optische Glaswerke G. m. b. H',Berlin-Zehlendorf, Germany Application June 5, 1934, semi No. '129,061

In Germany .lune '1, 1933- s claims. (ci. ca -39) The present inventionrefers to a magnifying glass which consists of one single 'glass bodyand is placed direct on the object tol be magnified, for instance onreading matter, fabric and the '5 like.

4Experience proves that it is necessary to provide the best possiblellluminationfor the surface to be magnified, because the perceptibilityofthe details of the object depends not only l upon linear magnificationbut, very much, also upon illumination. Magnifying glassesto be placedon the object direct are already known, but with all these glasses theillumination is neglected, importance being attached onlyto vl5 verystrong magnification and absence of vclistortion. y

To improve the illumination of the surface to be magnified,specialfsources of light have been used, or the lateral surfaces of aglass body of this kind to be placed on the object have been roughened.However, the use of a source of light complicates the instrumentto alarge extent and, on the other hand, rough surfaces entail thedisadvantage that onlya small part of the light they diffuseI reallystrikes the object to be magnied and thatA they are easily soiled andthus cause a further diminutionof luminous intensity. Moreover, theknown magnifying glasses are subject to the inconvenience that thegreater part of the light is kept away by the observers head, thespherical surface, which is next to the observer, therefore transmittingonly very little light to that part of the object which is to bemagnified. l

My invention overcomes all these dimculties without use being made ofany auxiliary means. I have found out that providing a lens of this kindwith a spherical surface ofA special construction and giving the glassbody of this lens 470 a denite medial thickness makes the spherical rsurface direct to theobject under examination twice the quantitylof.light striking those parts of the object which do not lie beneath thelens, experiments having provedthat a glass body which receives from allsides light through a convex surface in the form of a calotte whoseaperture is at anangle of approximately 70 relatively to the axis has aspot at which thel luminous intensity per superficial unit is greatest.The fact that the observers head is in the way of the light raysincident ,in the direction of the optical axis is only of secondaryimportance in l a lenshaving the said aperture.

I have discovered that light rays which enter` height in Another featureof my all sides cfabody'of this description notpenetrate the interior ofthis body uniformly,

and that all incident rays traverse at a definite this body a commoncross-sectional area, in which they are intensified. Accordingly, thelight rays traversing the glass body are constricted in the said area.and diverged to largerf `cross-sectional areas at greater thevspherical surface. .It is a feature of my invention that the lens bodyis given such` a medial thickness as to make the surface resting againstthe object to be. magnified lie in thatplane in which all light rayshave a common cross-sectional area. With a refractive index of forinstance 1.52, the medial thickness is greater than,

and at most equal to one and a half times,`the radius of curvature, themost favorable conditions being arrived at with a medial thickness of1.25 r. `With glasses of' other r'efractive indices and with artificialglasses, for instance pallopase, the distances corresponding to therespective refractive indices may be determined graphically ornumerically. A glass body having distances fro'm a bounding surface atthe place of the vgreatest constriction ofthe light provides the bestpossible luminous intensity for the object.

this that the convex entrance vsurface for the l"light is so dimensionedthat all light pencils which enter obliquely and assume angles'ofincidence of up to are made use of completely v for the illumination ofthe object. It is thereinvention consists in fore of importance thatthe-convex surface is not restricted in size by a vignette or recesses.

A further feature of my invention consists in this that that surfacewhich lies against the object to be magnified is slightly concave. andthis with a view to preventing its being scratched when placed on theobject. v

A further feature of my invention consists in providing a scale on thatsurface of the glass body which lies against the object.

A preferable constructional form of the object of myk invention isdescribed in detail with reference to the accompanying drawing.

In the accompanying drawing, hich illustrates my invention, Figure 1 isa schematlcal reproduction of the ray path through the longitudinalsection of a glass body having-a convex' light entrance surfaceaccording to my invention.vv

Figure 2 represents the view of the bare glass body representing a lens..1

Figure 3 illustrates the glass body according to Figure 2 in a mount.

Flgureishowsthetopviewofalenswithcircularcrosssection.

oblique light pencils 4 and 5 traverse the convex surface of the lensbody. The rays of the oblique llight; pencil 5, which is made use of atangles of incidence of 90, transverse the glass piece 2 within a fleld6, and those of the` oblique light.

pencil 4 traverse this piece within the field 'I, whereas the axiallyparallel rays are combined in the optical axis, the rays incident closeto the axis being converged at the focus 8. Figure 1 shows clearly thatthe rays of the oblique aswell as of the axially parallel ray pencilltra-verse a v common cross-sectional area in the plane of separationbetween I and 2. Also when the observers head stops down the axiallyparallel pencil I, this plane is exposed to a luminousintenslty which istwice as great as that in the glass body 2, at a greater distance fromthe convex entrance surface, because the diierent refracted pencils oflight separate from each other in this latter case. It is of importancethat the spherical calotte bounding the body I has a-free surface whichpermits to use for the illumination in the plane of separation I and 2also oblique rays which strike comparatively steeply up to angles of 90.Figure 1 also shows very clearly that the light pencils 8 and 'I in theknown magnifying glasses 1 t0 be placed direct on the objectilluminate-only a marginal zone when the axially parallel rays are shutoff.

Figure 2 shows a special constructional form of a lens according to myinvention. The spherical calotte is integral with a cylindrical part.

Figure 5. In Figure 4 is indicated a scale 9 pro.

vided on the lower surface of the lens.

I claim:

1. A magnifying glass to be placed direct on the body to be examined andwhose surface facing the observer is a calotte the aperture of which isat an angle of approximately relatively to the axis, the base of themagnifying glass body lying approximately at the place of greatestconcentration of all the pencils of light rays falling into the saidcalotte, the medial thickness of the glass body being greater than theradius of curvature and. at most equal to one-and-a-half times theradius of curvature. i

2. In a magnifying glass according to claim l, a scale disposed on thesurface which rests against the body to be magnified.

3. In a magnifying glass according to claim l,

a mount surrounding the lower portion of the' Blass body.

' GEORG JAECK'EL.

